The present invention relates to an apparatus and a method for processing digitally encoded audio data and features of related music management software.
The use of portable audio data players capable of playing digitally encoded audio data has become commonplace. In particular, relatively small handheld devices that can process digitally encoded audio data stored on solid state memory devices have become popular. Additionally, as demand has increased for higher data storage capacity in portable audio data players, another generation of players has been developed and is gaining popularity. These portable audio data players include miniaturized high capacity hard drives that are not as susceptible to skips and other similar problems as are typical hard drives used in personal computers (“PC”) and other applications.
In an audio data player, the digital audio data is loaded into a data storage device by first downloading the data to a PC from an audio CD, the Internet, or another digital audio device. The data is then usually compressed according to a selected encoding format and loaded into the data storage device associated with the audio data player.
The audio data is decompressed/decoded by the audio data player during playback according to the selected encoding format. A variety of encoding formats for compressing and decompressing audio data is available. As used hereinafter, the term encoding format refers to any encoding/decoding scheme that specifies the syntax and semantics of a compressed bitstream and how the bitstream must be decompressed for reproduction. Such encoding formats include, but are not limited to, MP3 and MP3 Pro.
The data structure used for MP3 files includes a sequence of interleaved header frames and data frames. Each header frame includes various fields of information that pertain to the data frame that follows, for example, the bit rate used for compressing the data frame that follows. While the compression ratio used for encoding the audio data file may be fixed (constant bit rate or “CBR”) or may vary frame to frame depending upon the complexity of the audio (variable bit rate or “VBR”), the amount of playback time represented by each frame remains the same for MP3 formatted files. Therefore, in a VBR file, the amount of data contained within each data frame will vary, thus presenting difficulties in displaying elapsed play time during playback, especially when forward or backward skipping during the playback of an audio data file. To solve this problem, audio data players generally develop a timekeeping map that must be precompiled prior to playback by reading all of the header frames of an audio data file. Unfortunately, the precompiling of a timekeeping map delays the commencement of playback once an audio data file is selected.
For MP3 encoded audio data files, the data file is prepended or appended with a special set of frames called an ID3 tag. The ID3 tag contains descriptive text and other data relevant to the audio data file. For example, the tag may include title, artist, album, year, comments, and genre. ID3 tag information is useful for searching, sorting, and selecting specific audio data files based on the information contained in the ID3 tag. Because ID3 tag information is often stored as textual characters, the information can be displayed on the display screen of an audio data player. Although such a user interface is useful for finding, selecting, and playing an individual audio data file, having to read the display can be distracting to a person using an audio data player while involved in an activity such as jogging or driving.
Most audio data players utilize a digital signal processor (“DSP”) for performing audio decoding, decompression, and other transformations of the audio data file. For example, the DSP can provide various preset equalization modes or other audio enhancing settings that are useful for quickly selecting a specific playback preference. For example, a preset DSP mode may be specified for specific audio genres such as rock, jazz, and pop. Selection of such preset DSP modes generally requires the user to change the DSP mode during playback by pressing a designated button or selecting the DSP mode from a display menu. However, it may be inconvenient or difficult for the user to select or reselect a particular DSP mode during playback, for example, if the user is exercising, or if the player is operating in a random mode wherein the play may select a different genre each time a new file is selected for playback.
Most PC-based audio data file management programs allow the user to create and edit playlists that can then be downloaded to a portable audio data player and used for playing a select sequence of audio data files. One such form of playlist typically associated with MP3 audio data files is known as an M3U list. An M3U playlist consists simply of a text file containing a numbered sequential list of paths or locations of data audio files included in the playlist. Thus, a playlist created on a PC and downloaded to an audio data player may be used to selectively play a sequence of audio data files that are contained in the data storage of the audio data player. However, audio data players generally do not allow a playlist to be created or edited on the audio player itself. Additionally, the M3U file format includes only the file location or path information and a comment field. Thus, the M3U file format does not contain other audio data file information such as the information contained in an ID3 tag of an MP3 audio data file.